A summary of research projects and publications dealing with mosquitoes, wetlands and urban ecology (as well as other Medical Entomology activities) by Dr Cameron Webb (University of Sydney & NSW Health Pathology)

Zika virus spreading explosively, says World Health Organisation (The Guardian). Coverage of statement by WHO Director General that the explosive outbreak of Zika virus in the Americas as “deeply concerning” and that an emergency committee has been convened. Click.

WHO Director-General summarizes the outcome of the Emergency Committee regarding clusters of microcephaly and Guillain-Barré syndrome (WHO). Click.

Zika Virus Spreads to New Areas — Region of the Americas, May 2015–January 2016 (CDC). Click.

WHO early response to Zika virus praised by Australian experts (The World Today). Click.

First report of autochthonous transmission of Zika virus in Brazil (Memórias do Instituto Oswaldo Cruz). Click.

How a Medical Mystery in Brazil Led Doctors to Zika (New York Times). A summary of how health officials investigating a spike in cases of birth defects put together the link to a mosquito-borne disease. Click.

Explainer: where did Zika virus come from and why is it a problem in Brazil? (The Conversation). A good, brief summary of the emergence of Zika virus in Brazil and the health risks it poses. Click.

Zika virus outbreak: What you need to know (New Scientist). A good summary of issues associated with Zika virus outbreak. Click.

Zika outbreak: What you need to know (BBC). A good summary of what is known of Zika virus and its health risks. Click.

Why it’s wrong to compare Zika to Ebola (The Conversation). Whats the difference between Ebola and Zika viruses? What are the implications of outbreaks and declarations of public health emergencies? Click.

Zika fever: panic won’t help us (The Guardian). Editorial highlighting the horror and unexpectedness of the Zika virus outbreak in Brazil and how we should move forward in mosquito control. Click.

What we still don’t know about Zika virus (Mashable). There are plenty of gaps in our understanding of Zika virus. Click.

The human cost of Zika is clear, but will Brazil’s economy suffer too? (The Conversation). Outbreaks of infectious diseases can have greater impacts than the human illness alone. Click.

Zika virus and its vectors

Mosquitoes: The Zika vector (Radio National). Why do we need to know how many mosquitoes can spread Zika virus and what is it about the mosquitoes that do that make them such an important pest? Click.

Natural-born killers: mosquito-borne diseases (SMH). What is it that makes mosquitoes such effective vectors of pathogens? Click.

Microcephaly in Brazil: is it occurring in greater numbers than normal or not? (Virology Down Under). Great post highlighting the gaps in our understanding of links between microcephaly and Zika virus. Click.

Proving that the Zika virus causes microcephaly (The Conversation). What questions must be answered to confirm a link between Zika virus and microcephaly. Click.

Zika Virus Infection In Australia Following A Monkey Bite In Indonesia (Southeast Asian Journal of Tropical Medicine and Public Health). Abstracted from published case report of suspected Zika virus infection following monkey bite. Click.

Six cases of Zika virus in Australia last year as pregnant women warned not to travel (SMH). Summary of recent imported cases of Zika virus infection in Australian travellers. Click.

Zika virus: following the path of dengue and chikungunya? (The Lancet). Good paper, including useful maps, of activity of three critical mosquito-borne pathogens. Click.

Rapid spread of emerging Zika virus in the Pacific area (Clinical Microbiology and Infection). Publication reporting on the 2013 outbreak of Zika virus in the Pacific. Click.

Notes on Zika virus – an emerging pathogen now present in the South Pacific (Australian and New Zealand Journal of Public Health). An article assessing the risks of Zika virus to New Zealand. Although no suitable vectors exist there, a relatively larger volume of infected travellers would be expected to occur given the strong links to Pacific Islands. Click.

Australia to help Pacific fight Zika (SBS News). How can Australian authorities take their expertise in mosquito monitoring, mosquito control and vaccine development to assist outbreak of Zika virus. Click.

Zika: Why the virus isn’t an STI despite being passed on after sexual contact (Independent). Only where sex is the predominant route of transmission, and the infection is maintained in the human population by sexual transmission, is a pathogen considered a STI and that definition does not apply to Zika virus. Click.

Zika Outbreak Means It Is Now Time To Cancel Rio Olympics (Forbes). Is the threat of Zika virus really so great that the Rio Olympics should be cancelled? Click.

NYU Bioethicist, Amid Zika Threat, Wants to Reschedule Rio Olympics: ‘What the Hell’s the Difference?’ (New York Magazine). With so many unanswered questions, and little confidence the outbreak is under control, is it really ethical to go ahead with the Rio Olympics? Click.

Bushman named as official insect repellent of Australian Olympic team (mUmBRELLA). One of Australia’s leading mosquito repellent manufacturers to support the athletes and officials travelling to Rio Olympics. Click.

Battling mosquitoes and the Zika virus outbreak

How Can We Slow The Epidemic Of Zika Infections? (Forbes). Now that the outbreak of Zika virus has been documented, what strategies are available to slow the spread and increasing numbers of cases? Click.

The world needs a Zika vaccine: Getting one will take years (STAT). We won’t have a Zika virus vaccine anytime soon. Here is an explanation why. Click.

Mosquito Wars Update: Would You Choose GMO ‘Mutants,’ Pesticides Or Dengue And Zika Viruses? (Forbes). The outbreak of Zika virus has focused the attention of health authorities on options for future mosquito-borne disease management strategies. Click.

Brazil sends in 200,000 soldiers to stop the spread of the Zika virus outbreak which has seen huge numbers of babies born with small heads and cast a shadow over the Olympics (Daily Mail). Click.

Here’s what it will take to stop the Zika virus (Vox). Summary of critical issues to address to better understand and stop the Zika virus outbreak. Click.

Curbing Zika Virus: Mosquito Control (Popular Science). Well supported article on options for mosquito control and mosquito-borne disease management. Click.

7 ways the war on Zika mosquitoes could be won (New Scientist). Overview of the different approaches available to beat the Zika virus outbreak and mosquito-borne disease more generally. Click.

In Australia, a New Tactic in Battle Against Zika Virus: Mosquito Breeding (New York Times). Overview of emerging technologies developed in Australia to battle dengue but could be incorporated into the Zika virus response. Click.

Zika virus: pesticides are not a long-term solution says leading entomologist (The Guardian). Spraying insecticides can sometimes be a blunt instrument unless there is an understanding of where best to target mosquito populations. Click.

Zika outbreak revives calls for spraying with banned pesticide DDT (STAT). Outbreaks of mosquito-borne disease often prompt calls to return to DDT as teh insecticide of choice to control mosquitoes. Click.

Insecticide to be sprayed inside planes from Zika affected regions (The Guardian). Aircraft should already be treated with insecticides to stop movement of mosquitoes from one country to the next, hitchhiking in planes but efforts have been boosted in wake of Zika virus fears. Click.

Let’s Kill All the Mosquitoes (Slate). Emergence of another mosquito-borne disease, another opportunity to call for killing mosquitoes off completely. Click.

Why Eradicating Earth’s Mosquitoes To Fight Disease Is Probably a Bad Idea (Vice). Don’t be so sure that eradicating mosquitoes is the answer, or at least it won’t have consequences. Click.

Would it be wrong to eradicate mosquitoes? (BBC). What could be the unexpected consequences of sending mosquitoes extinct? Click.

Sights on world’s deadliest animal as Zika virus spreads (The New Daily). Wiping out all mosquitoes is probably a bad idea but perhaps we could knock off just a few and greatly improve the health of the planet? Click.

They’re small, spindly insects but their threat never dwindles – the bites of mosquitoes threaten death and disease in many parts of the world. The emergence of a little-known virus, Zika, from an African forest, is the latest to alarm the public, politicians and health authorities because of its potential link to birth defects.

What is Zika virus?

Zika virus is a mosquito-borne virus closely related to dengue and Yellow Fever viruses. Discovered almost 70 years ago in a Ugandan forest, the virus generally only causes a mild illness. Symptoms include rash, fever, joint pain and conjunctivitis.

Severe symptoms aren’t common and the illness was never thought to be fatal.

Despite detection throughout Africa and Asia, the virus rarely entered the spotlight of scientific research. It was overshadowed by the spread and impact of dengue and chikungunya viruses, which infect millions of people across the regions.

New outbreaks and severe symptoms

Since the first local Zika virus infection, cases have been reported from at least 19 countries or territories in the Americas, with more than one million suspected cases.

Rapid spread of an emerging mosquito-borne pathogen is news enough but people are also panicked by reports of more serious consequences of Zika virus infections, including post-viral Guillain-Barré Syndrome, an autoimmune condition where there person’s nerves are attacked by their own body.

Of most concern has been the rapid rise in rates of microcephaly, a birth defect which causes babies to be born with unusually small heads, in regions where Zika virus has been circulating.

While the role of Zika virus as the cause of microcephaly has not yet been confirmed, there is growing evidence of a connection between the two where pregnant women have been infected with the virus.

Babies born with microcephaly, and those who died shortly after birth, have tested positive for the virus, and there are close regional associations between clusters of birth defects and Zika virus.

There is no vaccine for Zika virus. Stopping mosquito bites is the only way to prevent infection.

Is Australia at risk of a Zika virus outbreak?

There is little doubt the virus can make it to Australia. There have already been a number of infections reported in travellers arriving in Australia from the Cook Islands and Indonesia.

Mosquito-borne viruses generally aren’t spread from person to person. Only through the bite of an infected mosquito can the virus be transmitted.

In the case of Zika, there have been some unusual cases of transmission, including through sex and the bite of an infected monkey. Despite these unusual circumstances, mosquitoes will still play the most important role in any local transmission.

While dozens of mosquitoes are capable of spreading local mosquito-borne pathogens, such as Ross River virus, only one of the 300 or so mosquitoes found in Australia can transmit Zika virus: Aedes aegypti, the Yellow Fever Mosquito, which is only found in north Queensland.

The Yellow Fever mosquito, Aedes aegypti, is critical to the spread of Zika virus in many regions of the world, including Australia.

For local Aedes aegypti to spread Zika virus, they must bite an infected traveller shortly after they return from a country where the virus is circulating.

While the chances of this happening are small, there is then a risk of a local outbreak occurring as the infected mosquito bites people who’ve never left the country.

This is the process that occurs in outbreaks of dengue in Far North Queensland. If we can get outbreaks of dengue, there is no reason we cannot, or won’t, get an outbreak of Zika in the future.

How to reduce the risk of transmission

Fortunately, authorities are well placed to contain an outbreak of Zika virus, as the required strategies are the same as management of dengue outbreaks.

Perhaps the real message here for Australian authorities is that they need to work diligently to keep exotic mosquitoes out of the country.

While Aedes aegypti may not become established in southern cities, even with a changing climate, there is great potential that Aedes albopictus, better known as the Asian Tiger Mosquito, could become established in southern cities. As well as a vector of Zika virus, it can spread dengue and chikungunya viruses and be a significant nuisance-biting pest. Keeping this mosquito out of our cities is critical.

Australians planning travel to South and Central America, including the Rio Olympics, should take precautions to avoid mosquito bites. Irrespective of Zika virus, mosquito-borne dengue and chikungunya viruses have infected millions of people, causing thousands of deaths, in the last few years and are reason alone to pack mosquito repellents. Be prepared to cover up with long sleeved shorts and long pants if in regions where risk is high.

There are millions of cases of mosquito-borne disease world wide every year so why should we care about a few dozen dengue cases in Hawaii?

Hawaii is no stranger to dengue. There have been outbreaks first dating back to the 1840s. Travellers, including returning residents, are diagnosed with dengue routinely. However, this is the first outbreak of locally-acquired infection since 2011.

As of 17 November 2015, Hawaii Department of Health reports there have been approximately 65 locally acquired cases on Hawaii Island (aka Big Island) including both residents and visitors. Why has this happened and what lessons can be learned from the outbreak?

[update: As of 29 January 2016, there have been 242 confirmed cases of locally acquired dengue.]

The first mosquito to make it to Hawaii was Culex quinquefasciatus. It is thought to have arrived on a boat from Mexico in the mid 1820s. Interestingly, with no native mosquitoes in Hawaii, there was no word to describe them so they were initially referred to as “singing flies”.

In recent years, it has been the role of Culex quinquefasciatus in the spread of avian malaria that’s been grabbing the headlines. However, in the last few weeks, it has been Aedes aegypti and Aedes albopictus playing a role in the local spread of dengue virus in the spotlight. These two container-inhabiting mosquitoes are the key vectors of dengue viruses (as well as chikungunya, yellow fever and zika viruses) internationally. They’re driving the outbreak now as they have in the past.

There was an outbreak of dengue in 2001 with a total of 122 locally acquired cases. Cases were reported from Maui, Oahu and Kauai with the outbreak thought to have been triggered by travellers from French Polynesia where there was a major outbreak underway at the time. Between 1944 and 2001, the only cases of dengue reported in Hawaii were imported with travelers. Firstly, this highlights how important it is to understand the pathways of infected people, this can help guide assessments of risk.

It was believed that Aedes albopictus played an important role in this 2001 outbreak. This mosquito was not a significant presence in Hawaii until the 1940s. More importantly, Aedes albopictus is not exclusively found in water-holding containers in urban area. Unlike the other vector of dengue viruses, Aedes aegypti, Aedes albopictus is also found in bushland habitats. This makes mosquito control just a little more difficult when authorities need to look beyond the backyard.

Previous dengue outbreaks in Hawaii were thought to have been driven by Aedes aegypti. These outbreaks were significant with an estimated 30,000 cases in the early 1900s followed by approximately 1,500 cases around Honolulu in the period 1943-1944. While not necessarily easy to manage, outbreaks of dengue driven primarily by Aedes aegypti can be strategically targeted by residual insecticide treatments and community education. That education focuses on raising awareness of the public health risks associated with mosquitoes and the need to remove opportunities for mosquitoes to be breeding around dwellings. This model is essentially what is in place to address occasional outbreaks of dengue in Far North Queensland, Australia.

The current outbreak has raised concern in the community. Shelves of stores have been emptied of insecticides and repellents. Community meetings have been held by local authorities to provide information on dengue and address concerns on the Big Island. You can watch some of the meetings here. You can see some of the health promotion (aka “Fight the Bite”) flyers here.

Community engagement is important. An indirect impact of this engagement though is that the total number of confirmed cases of dengue on the Big Island is likely to rise over coming weeks. Not necessarily due to new cases but a greater likelihood that older cases will now be diagnosed through blood tests. Even those who may be suffering a mild illness are likely to be tested for infection and may end up in official statistics.

This dengue outbreak is a reminder to authorities across the world that where suitable mosquitoes are present, a risk of mosquito-borne disease outbreak is possible. The mosquitoes provide the tinder and it only takes the spark of an infected traveler to ignite an outbreak. We saw this in 2014 with the first outbreak of dengue in Japan for 70 years. We’ve seen it this year with local transmission of chikungunya virus in Spain and other outbreaks across Europe.

For Australian authorities, ensuring there are strategic responses in place to address the risk of exotic mosquito introduction, as well as outbreaks of disease, is critical. What this outbreak in Hawaii reminds us is that if Aedes albopictus becomes established in our major cities, it is only a matter of time before we see local outbreaks of dengue, chikungunya or Zika viruses.

[Update: Implications for potential Zika virus spread] The recent spread of Zika virus in the Americas has raise concerns by health authorities. In particular, the spread of the virus to North America. What about Hawaii? There has already been one case of microcephaly in Hawaii with a baby born on Oahu to a mother who had been residing in Brazil. The pregnant women was infected in South America, not Hawaii. However, authorities should be on alert as travellers from the Americas, or the Pacific, have the potential to introduce the virus and the mosquitoes currently present in Hawaii spreading dengue viruses are the same that spread Zika virus.